The Vented Dual Check Valve (VDC) is used on carbonated beverage machines and prevents the reverse flow of polluted water such as carbon dioxide gas and carbonated water from entering into the potable water supply due to backpressure backflow. We strongly recommend that an RP be installed to the water supply of the soft drink carbonator. CO2 under pressure could create backpressure through the drinking supply line. The acidic carbonated water may leach out of the copper piping to cause gastrointestinal distress, vomiting or diarrhea. (ASSE 1022 or 1032)